The invention relates to a process for triggering passenger protection systems using at least two stages of an accident hazard or force.
Such processes are known for example from DE 42 20 270 A1, DE 43 24 753 A1 and DE 197 40 019 A1. In all these processes, passenger protection systems are triggered in at least two different stages of an accident hazard and/or accident force, determined in relation to sensor signals, with the passenger protection systems being triggered by a direct trigger command at least when the second stage of the accident hazard and/or accident force is reached. In order to generate the sensor signals describing the actual accident hazard and/or accident force, deformation sensors with a capability to respond particularly early to an accident, and located on external vehicle areas, are used in addition to acceleration-sensitive sensors. Furthermore, a process is known from DE 197 29 960 A1, for example, which triggers passenger protection systems by taking into account so-called precrash sensors that register any change in the relative distance and/or relative speed of objects within the immediate vicinity of the vehicle environment, and which in the event of a safety critical approach being detected, particularly in the case of an unavoidable collision, already generate a relevant sensor signal in line with the accident hazard. In relation to such a precrash sensor signal, passenger protection systems are triggered either directly or after further sensor signals have been taken into account, in particular the course of acceleration, with the trigger threshold causing a system to be triggered being possibly lowered in the case of a prior precrash signal.
In this case the precrash signal is assigned to a first accident hazard stage and reaching a relevant trigger threshold of the acceleration signal is assigned to the second stage of the accident hazard and/or accident force.
In addition, from DE 199 30 065 A1 for example, a process is also known for controlling passenger protection systems where it is only the acceleration signal that is evaluated in several stages, leading to an appropriately staged triggering of these systems.
In connection with the passenger protection systems located in a distributed arrangement around the vehicle there is always the fundamental question as to a safe and troublefree transmission of data to these passenger protection systems. For this reason, a number of applicationsxe2x80x94for example, DE 198 13 952 A1 and DE 195 03 460 C1xe2x80x94concern themselves with the error redundant data transmission within the bus system of passenger protection systems. Here, in the event of a short circuit to ground or a supply potential, data transmission is adapted by appropriate signalization.
However, in the event of a complete separation/cutoff of signal carrying lines during the course of an accident, it will not be possible in any case whatever to trigger the passenger protection systems that have been cut off in this way.
Therefore, it is the task of the invention to state a process for triggering passenger protection systems by means of which a still further improved protection for passengers is achieved.
This task is achieved according to the invention in a method of the above mentioned general type, further having the following special features.
To this end, when a first accident hazard and/or accident force stage is reached, an indirect trigger command is sent at least to individual passenger protection systems, that is, a trigger command which does not immediately cause a system to be triggered. This indirect trigger command can be issued directly by the sensors for determining the accident hazard and/or accident force, inasmuch as these feature a relevant direct connection to a common bus system, or by a central processing unit interrogating these sensors. A specified time interval is started, and in the event of the second accident hazard or accident force stage not being reached within the specified time interval, a cancel command is sent which cancels again the indirect trigger command, i.e. undoes the same.
On receipt of such an indirect trigger command the respective passenger protection systems also start a relevant time interval, and in the event of the cancel command not being received within this time interval, i.e. on expiry of the said interval, the respective passenger protection systems are triggered.
In this way, it is possible to ensure that any crash-induced separation of the passenger protection system from the bus system, which occurs after the first accident hazard and/or accident force stage has been reached, will still provide for the separated passenger protection system to be triggered.
In comparison to a time-delayed triggering when all communication with the central processing unit or the sensors has been lost, and where it is also not possible to take into account an actual accident hazard and/or accident force, this process provides the security that the passenger protection systemsxe2x80x94separated from the bus system during the course of the accidentxe2x80x94are triggered only if an actual accident hazard and/or initial accident stage is detected.
If the risk falls below the first accident hazard and/or accident force stage, the cancel command is preferably sent immediately to stop the indirect triggering of the respective passenger protection systems, that is, the time-delayed triggering of the said systems in accordance with the specified time interval. In addition to sending a cancel command, if the first accident hazard and/or accident force stage is still reached as before, it is possible to resend a new indirect trigger command at a time within the specified time interval by means of which command the time intervals in the central processing unit or the sensors, on the one hand, and in the passenger protection systems on the other, are restarted so thatxe2x80x94if there is no change in the applicable first accident hazard and/or accident force stagexe2x80x94a decision on whether to trigger or not to trigger can be delayed even beyond the duration of a time interval, with the respective passenger protection systems always being triggered in the event of the data transmission being disconnected due to an accident event.
In principle, it is also conceivable that more than just two stages of accident hazard and/or accident force are provided for, with the various individual passenger protection systems being allocated a lower stage and a higher stage, respectively, in line with the first and second stages. If, for example, individual passenger protection systems are triggered only when a third stage of accident hazard, or rather accident force, has been reached, a lower stagexe2x80x94that is, the first or second accident hazard or accident force stagesxe2x80x94may give an indirect trigger command in identical fashion, which, when data connections are interrupted, will cause the respective passenger protection systems to be triggered on expiry of the time interval without the relevant cancel command or a renewed indirect trigger command having been received.